It has been known for some time to produce company brochures, financial reports, marketing documents, or the like by binding the sheet stack that reproduces the contents into a binder that comprises a binder spine and binder covers continuous therewith. For that purpose, the binder spine has on the inner side an adhesive strip made of hot-melt adhesive. For binding, the combination of sheet stack and binder is put into a binding apparatus embodied as an office machine, and the binder spine is heated sufficiently that the hot-melt adhesive strip becomes plasticized and the ends of the sheet stack in contact therewith sink into the hot-melt adhesive strip. After removal of the combination, the hot-melt adhesive strip cools and thereby forms a permanent bond between the sheet stack and the binder.
Binders of this kind are known, for example, from U.S. Pat. No. 3,437,506, DE Pat. 25 28 225, U.S. Pat. No. 4,244,069, U.S. Pat. No. 4,289,330, and EP 0 410 197 B1. Binding apparatuses suitable for binding are evident from DE Examined Application 22 56 259, U.S. Pat. No. RE 28,758, U.S. Pat. No. 3,973,778, U.S. Pat. No. 4,129,471, U.S. Pat. No. 4,141,100, DE 38 05 996 C2, and EP 0 581 394 B1. All the binding apparatuses are configured in such a way that the combination of sheet stack and binder is inserted into an input slot that is open at the top, so that the outer side of the binder spine faces downward. The binder spine is placed on a heating plate that closes off the input slot at the bottom, and is heated by that plate. To ensure that the combination maintains its vertical position, the binding apparatus comprises a pressing device that compresses the combination and holds it in the upright position. The pressing device is, as a rule, embodied in such a way that at least one of the side walls delimiting the input slot is guided displaceably relative to the others, so that the width of the input slot can be modified and the combination can be held pressed between the two side walls.
In one method of the species (U.S. Pat. No. 4,141,100), a binder is used that comprises on the inner sides of the binder covers, in the vicinity of the binder spine, strips that are triangular in cross section and that extend parallel to the binder spine and are located opposite one another. Upon compression of the sheet stack by displacement of one of the two side walls of the input slot toward the other side wall, the sheet stack is intended thereby to be compressed in the region of the strips in order to hold the sheets of the sheet stack in their aligned position, and their lower edges in contact with the adhesive strip. Since compaction of the combination occurs above the strips, however, considerable doubt exists that the sheet stack is compressed—and the end face resting against the adhesive strip thus fanned out—in the manner depicted in FIG. 7 of U.S. Pat. No. 4,141,100. It may rather be assumed that the binder covers bulge outward in the region of the strips, and that the desired purpose is thus achieved not at all or at any rate incompletely.
In the method according to U.S. Pat. No. 3,973,787, binders are used in which the binder spine and also the adhesive strip are wider than the end face, resting thereagainst, of the sheet stack provided for the purpose. For binding, the combination of sheet stack and binder is inserted into the input slot of a binding apparatus in which the two side walls are movable toward one another for the purpose of contact against the outer sides of the binder covers. Arranged at each of the lower ends of the side walls near the heating plate is a respective roller that is resiliently suspended on the side walls. Upon compaction of the combination, these rollers first come into contact against the outer sides of the binder covers, thus ensuring that the externally located sides of the sheet stack have good contact with the adhesive strip. The binder cover is, in this context, pushed against the outer sides of the sheet stack. Only after that do the side walls of the input slot come to rest against the outer sides of the binder covers.
The known binding methods that are carried out using the binders and binding apparatuses recited in the documents have the disadvantage that the adhesive bond is not as strong as is necessary, at least when greater stresses are applied. Since these methods are used to produce brochures that are often representative in nature, it is essential that the brochures not fall apart even after repeated use.